1. Field of the Invention
This invention relates generally to the structure of electrochemical storage batteries, and more particularly, to a novel and improved electrode plate for such batteries.
2. Description of the Related Art
Typically, storage batteries of the electrochemical type have one or more cells which include a plurality of first electrodes of one polarity interleaved in a spaced apart manner with a plurality of second electrodes of the opposite polarity. Separate terminals interconnect the electrodes of each polarity, usually to a terminal post, so that two terminals of opposite polarity are provided for each cell.
U.S. Pat. No. 5,158,842 discloses the basic structure of a storage battery having a plurality of interleaved electrode plates of opposite polarities. Each of the plates has a generally rectangular main section that forms an active region of the electrode with a tab projecting outward from one corner of the main section. The tabs of the electrode plates of one polarity are aligned along one side of the battery, while the tabs on the opposite polarity plates are aligned on the other side of the battery. The respective tabs of the plates of the same polarity are electrically connected, such as by welding, to the body of a terminal that has a connection post.
One type of electrode plate comprised a flexible fiber plaque that was suitable for active material loaded electrodes, such as used in nickel-cadmium and nickel-iron battery systems. A common fibrous plaque was made of compacted, intermingled fine fibers reactively diffused with nickel by conventional plating processes. Prior batteries had plaques that often were formed by conductive fibers, such as iron wool, however non-conductive fibers also were used. The fibers were randomly oriented in the length, width and thickness directions of the plaque and are diffusion bonded with nickel at their contact points. The resultant electrode had pores into which the active material of the battery was introduced during subsequent assembly steps.
As shown in FIG. 1, a typical previous electrode 10 was rectangular—having one edge that was significantly greater than another orthogonal edge. The electrode 10 has a sheet-like body 11 comprising a main, or active, region 12 and a tab 16. The main region 12 had a uniform electrical conductivity. The tab 16 projected from the longer edge of the main section 12 and due to the electroplating process that tab had a portion 14 with greater density of metal. That portion 14 enabled a metal contact tab 18 to be welded to the electrode body 11. In the final battery, a battery terminal was welded or otherwise electrically connected to the contact tabs 18 of the electrodes 10 of the same polarity, thereby connecting those electrodes together.
Certain battery installations dictated that the terminals be placed along the shorter edge of the electrode with the edge extending perpendicularly there from having a significantly greater length. However, it was discovered that in this orientation the effective resistance in the portion of the electrode remote from the tab was significantly greater than the portion of the electrode adjacent the tab. Thus, the more distant portion of the electrode was less effective than the portion closer to the tab.